This Buick quits while driving.

Gm products back then were known for ignition switch problems, also check the power distribution box for any signs of overheating.

check applicable fuse tangs for tarnish , could be an indication of excessive heat/voltage or poor connection

As it turns out, after excessive time spent diagnosing, the PCM/ECU is bad. It would start up and run great, until it the coolant reached 200 Degrees and then things would start to go haywire. Some of the gauges (fuel, coolant, and security light) would either go full or bottom out. It wouldn't restart until the gauges went back to normal and then it would cut back out again. The vehicle wouldn't communicate with the scan tool until things cooled down too. Sorry this answer is so long but there's even more stuff I could post but bottom line, it needs to go to dealer for pcm and program.